1. Field of the Invention
The present invention relates to novel polyethylene which has a branching structure. The present invention also relates to a process of production of the novel polyethylene.
2. Related Background Art
Generally, polymerization of ethylene with a free radical initiator at exceedingly high temperature and pressure gives polyethylene which has long chain branches having length comparable to the main polymer chain thereof. On the contrary, polymerization of ethylene with a Ziegler-Natta catalyst gives polyethylene which has almost no branches.
In order to produce branched polyethylene by use of a Ziegler-Natta catalyst, ethylene is generally copolymerized with .alpha.-olefin. The copolymerization, however, does not give long chain branches as those formed by radical polymerization.
In an attempt to obtain low-pressure polyethylene having such long chain branching, ethylene is oligomerized by use of a nickel catalyst such as disclosed in Japanese Patent Application Laid-Open No. 63-12607, and the resulting oligomer is copolymerized with ethylene in the presence of a chromium catalyst. This method does not give such a long chain branching as produced by free radical polymerization.